Make HostManager track NUMA usage

This patch adds tracking of NUMA usage in scheduler's HostManager class,
by adding it to the HostState, and making sure it gets updated along
with all the other usage data.

Change-Id: Id31c9a7fd54b918b3d38abb61b305cf7048a6a7d
Blueprint: virt-driver-numa-placement
Add the NUMATopologyFilter

This patch adds the basic NUMA filter that will take the proposed
instance topology and try to match it against that of a host.

The matching will be done in the following manner:

 * Filter will try to match the exact NUMA cells of the instance to those
   of the host. It *will not* attempt to pack the instance onto the host.
 * It will consider the standard over-subscription limits for each cell,
   and provide limits to the compute host accordingly.
 * If instance has no topology defined, it will be considered for any host.
 * If instance has a topology defined, it will be considered only for NUMA
   capable hosts.

DocImpact

Change-Id: I8788dde69524c8a32a41ce31a96c89f9b09e91ce
Blueprint: virt-driver-numa-placement
libvirt: Consider numa_topology when booting

This patch hooks all the already introduced pieces together to enable
NUMA aware placement of instances.

The libvirt driver boot process now looks into the NUMA topology field
of both instance and the host it is being booted on, and based on that
adds some more configuration to the generated guest XML.

In case the host is NUMA capable, but the instance has not requested
a NUMA topology, we will try to pack the instance into a single cell.
If that fails, currently we will not make further attempts (although
an improvement could be to expose the underlying topology to the
instance).

In case the host is NUMA capable, and instance has requested a specific
NUMA topology, we will try to pin the vCPUs of different instance NUMA
cells to the corresponding host NUMA cells, and also expose the instance
NUMA topology to the guest OS.

We will still try to respect CONF.vcpu_pin_set option and avoid pinning
to CPUs that are not in this set.

DocImpact

Change-Id: I611d44ab75475028f63c2b7f8a0d2ef37d85be6e
Blueprint: virt-driver-numa-placement
Merge "Make HostManager track NUMA usage"
Merge "Add the NUMATopologyFilter"
Merge "libvirt: Consider numa_topology when booting"